From c704491d7921156419609e08c64ab3c64de2e20f Mon Sep 17 00:00:00 2001
From: neauoire <aliceffekt@gmail.com>
Date: Sun, 10 Apr 2022 09:42:56 -0700
Subject: [PATCH] Allow the system device to handle errors

---
 src/devices/system.c | 22 +++++++++++++---------
 src/uxn.c            | 12 ++++--------
 src/uxn.h            |  4 ++--
 3 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/src/devices/system.c b/src/devices/system.c
index c3023eb..bcd980a 100644
--- a/src/devices/system.c
+++ b/src/devices/system.c
@@ -15,12 +15,9 @@ WITH REGARD TO THIS SOFTWARE.
 */
 
 static const char *errors[] = {
-	"Working-stack underflow",
-	"Return-stack underflow",
-	"Working-stack overflow",
-	"Return-stack overflow",
-	"Working-stack division by zero",
-	"Return-stack division by zero"};
+	"underflow",
+	"overflow",
+	"division by zero"};
 
 static void
 system_print(Stack *s, char *name)
@@ -42,10 +39,17 @@ system_inspect(Uxn *u)
 }
 
 int
-uxn_halt(Uxn *u, Uint8 error, Uint16 addr)
+uxn_halt(Uxn *u, Uint8 instr, Uint8 err, Uint16 addr)
 {
-	system_inspect(u);
-	fprintf(stderr, "Halted: %s#%04x, at 0x%04x\n", errors[error], u->ram[addr], addr);
+	Stack *origin = (instr & 0x40) ? u->wst : u->rst;
+	Uint8 *d = &u->dev[0x00];
+	origin->err = err;
+	if(GETVEC(d))
+		uxn_eval(u, GETVEC(d));
+	else {
+		system_inspect(u);
+		fprintf(stderr, "%s %s, at 0x%04x.\n", (instr & 0x40) ? "Return-stack" : "Working-stack", errors[err - 1], addr);
+	}
 	return 0;
 }
 
diff --git a/src/uxn.c b/src/uxn.c
index 90cd236..9436e14 100644
--- a/src/uxn.c
+++ b/src/uxn.c
@@ -16,8 +16,8 @@ WITH REGARD TO THIS SOFTWARE.
 #define PUSH8(s, x) { if(s->ptr == 0xff) { errcode = 2; goto err; } s->dat[s->ptr++] = (x); }
 #define PUSH16(s, x) { if((j = s->ptr) >= 0xfe) { errcode = 2; goto err; } k = (x); s->dat[j] = k >> 8; s->dat[j + 1] = k; s->ptr = j + 2; }
 #define PUSH(s, x) { if(bs) { PUSH16(s, (x)) } else { PUSH8(s, (x)) } }
-#define POP8(o) { if(!(j = *sp)) { errcode = 0; goto err; } o = (Uint16)src->dat[--j]; *sp = j; }
-#define POP16(o) { if((j = *sp) <= 1) { errcode = 0; goto err; } o = src->dat[j - 1]; o += src->dat[j - 2] << 8; *sp = j - 2; }
+#define POP8(o) { if(!(j = *sp)) { errcode = 1; goto err; } o = (Uint16)src->dat[--j]; *sp = j; }
+#define POP16(o) { if((j = *sp) <= 1) { errcode = 1; goto err; } o = src->dat[j - 1]; o += src->dat[j - 2] << 8; *sp = j - 2; }
 #define POP(o) { if(bs) { POP16(o) } else { POP8(o) } }
 #define POKE(x, y) { if(bs) { u->ram[(x)] = (y) >> 8; u->ram[(x) + 1] = (y); } else { u->ram[(x)] = y; } }
 #define PEEK16(o, x) { o = (u->ram[(x)] << 8) + u->ram[(x) + 1]; }
@@ -82,7 +82,7 @@ uxn_eval(Uxn *u, Uint16 pc)
 		case 0x18: /* ADD */ POP(a) POP(b) PUSH(src, b + a) break;
 		case 0x19: /* SUB */ POP(a) POP(b) PUSH(src, b - a) break;
 		case 0x1a: /* MUL */ POP(a) POP(b) PUSH(src, (Uint32)b * a) break;
-		case 0x1b: /* DIV */ POP(a) POP(b) if(a == 0) { errcode = 4; goto err; } PUSH(src, b / a) break;
+		case 0x1b: /* DIV */ POP(a) POP(b) if(a == 0) { errcode = 3; goto err; } PUSH(src, b / a) break;
 		case 0x1c: /* AND */ POP(a) POP(b) PUSH(src, b & a) break;
 		case 0x1d: /* ORA */ POP(a) POP(b) PUSH(src, b | a) break;
 		case 0x1e: /* EOR */ POP(a) POP(b) PUSH(src, b ^ a) break;
@@ -90,12 +90,8 @@ uxn_eval(Uxn *u, Uint16 pc)
 		}
 	}
 	return 1;
-
 err:
-	/* set 1 in errcode if it involved the return stack instead of the working stack */
-	/*        (stack overflow & ( opcode was STH / JSR )) ^ Return Mode */
-	errcode |= ((errcode >> 1 & ((instr & 0x1e) == 0x0e)) ^ instr >> 6) & 1;
-	return uxn_halt(u, errcode, pc - 1);
+	return uxn_halt(u, instr, errcode, pc - 1);
 }
 
 /* clang-format on */
diff --git a/src/uxn.h b/src/uxn.h
index fa9a216..58339af 100644
--- a/src/uxn.h
+++ b/src/uxn.h
@@ -26,7 +26,7 @@ typedef unsigned int Uint32;
 /* clang-format on */
 
 typedef struct {
-	Uint8 dat[255], ptr;
+	Uint8 dat[254], err, ptr;
 } Stack;
 
 typedef struct Uxn {
@@ -38,4 +38,4 @@ typedef struct Uxn {
 
 int uxn_boot(Uxn *u, Uint8 *ram);
 int uxn_eval(Uxn *u, Uint16 pc);
-int uxn_halt(Uxn *u, Uint8 err, Uint16 addr);
+int uxn_halt(Uxn *u, Uint8 instr, Uint8 err, Uint16 addr);